(1) Field of the Invention
This invention relates to a foamed product made by combining biodegradable cellulose fibers material and a superabsorbent polymer. More specifically, this invention relates to a foamed product made from cellulose fibers and a superabsorbent polymer, which is especially useful as a cushioning material, and to methods of making the foamed products.
(2) Description of the Prior Art
The prior art is replicate with products useful as cushioning or packaging material. These products are generally known as dunnage material. When shipping articles, especially fragile articles, it is desirable to make sure that the articles are safely packaged using dunnage material in one form or another. Dunnage materials include such things as bubble paper, styrofoam pellets, commonly known as "peanuts", ordinary tissue paper, embossed paper, foamed in place plastic materials and the like. While all of these dunnage materials provide a certain effectiveness as packaging materials, they are not universally suitable for every packing need.
Additionally, because disposal of waste paper in an increasing problem in our society, it is desirable to find beneficial uses for waste paper and certain other biodegradable fibrous materials. Reusable and biodegradable dunnage material provides a valuable use. Of course, there have been attempts to convert newsprint and other waste paper into useful products. Among the difficulties encountered in attempts to convert waste newsprint into useful products is newsprint's short length fibers and low potential strength.
There have also been disclosed numerous ways to form sheets of absorbent material from wood fibers and superabsorbent polymers. In such products, the wood fibers and the superabsorbent polymer are fixed in place mechanically and embossed to mechanically set in place the superabsorbent polymer. The thus formed product is used to absorb water or other liquid material. Such products have for years been converted into products to increase the absorbency such as diapers, sanitary napkins, absorbent cloths and pads, and the like. For example, one such product is disclosed in EPO Patent Application 255,654, wherein there is described an approach to making sheets of fibrous material in which cellulose fibers and superabsorbent polymers in the form of fibrils are formed into dry sheets. The fibers and superabsorbent polymer are suspended in an air stream of a mixture of fibers and polymer and dry formed onto one face of a moving permeable forming surface and hot calendaring or embossing to bind the materials.
Other approaches for combining cellulose fibers and superabsorbent polymers have been proposed. Some of these approaches use binders to attach the superabsorbent polymer and fibers together to make products useful for absorbing liquids. One such approach is set forth in PCT application WO 90/1181 which discloses coating fibers with at least about 7% by weight of one or more one or more liquid binders and applying a superabsorbent polymer to the fiber while the liquid binder on the fiber is still at least partially wet to uniformly adhere to the fibers.
The various products formed from combining cellulose fibers and superabsorbent polymers have been found useful as absorbent wipes or converted into other products but they have not been designed to meet the specific needs of the packaging industry.